1. Field of the Invention
The present invention relates to a printing relief plate provided on the surface of a plate material, and on which convexities are formed for transferring inks to a print medium to print halftone dots thereon. Further, the present invention relates to a printing relief plate producing apparatus and a printing relief plate producing method for producing the aforementioned printing relief plate. Furthermore, the present invention also relates to a printing apparatus and a printing method for transferring inks from the printing relief plate to a print medium to print halftone dots thereon. Still further, the present invention relates to a printing pressure determining apparatus and a printing pressure determining method for determining whether or not a printing pressure applied to a printing relief plate is an appropriate printing pressure in a case where ink is transferred to a print medium from the printing relief plate.
2. Description of the Related Art
For example, in flexographic printing, a printing relief plate, which is made from a flexible plate material having elasticity, is mounted on the surface of a plate cylinder. Convexities for printing halftone dots by transferring ink to a print medium are formed on a surface (plate surface) of the printing relief plate. Then, in the case that ink is supplied to a plate surface from an anilox roller, under a condition in which the print medium is gripped by the plate cylinder and an impression cylinder, the ink is transferred to the print medium from the plate surface, and halftone dots can be printed on the print medium. Consequently, a desired image can be transferred to (printed on) the print medium.
In this case, by adjusting the pressure (anilox pressure) between the anilox roller and the plate surface, and the pressure (printing pressure) between the plate surface and the print medium, printing conditions for the print medium can be determined. Further, for satisfactorily transferring the entire image (image pattern) to the print medium, preferably, the printing pressure is kept as low as possible (at a minimum printing pressure necessary for favorably transferring the entire image).
Japanese Patent No. 4962855 discloses a technique wherein a detecting portion, which is lower than an image printing area made up of convexities, is formed on a plate surface, and in the case that ink from the detecting portion is transferred to the print medium, it is determined that an excessive printing pressure (also referred to below as an over-printing pressure) is applied onto a plate surface.
Further, Japanese Laid-Open Patent Publication No. 02-009635 and Japanese Laid-Open Patent Publication No. 2009-000881 disclose techniques for adjusting a printing pressure, based on a line width or density of a linear portion, which is printed on a print medium.
Furthermore, Japanese Laid-Open Patent Publication No. 2002-137558 discloses a technique of inspecting the quality of a printing relief plate, by confirming an image that is transferred to a print medium by transfer of ink to the print medium from quality-confirming convexities that are formed on the plate surface.